1. Field of the Invention
This invention relates to overrunning coupling assemblies and methods for controlling the engagement of planar members.
2. Background Art
Overrunning coupling assemblies may be used for transferring torque from a driving member to a driven member in a variety of structural environments. This permits the transfer of torque from a driving member to a driven member while permitting freewheeling motion of the driving member relative to the driven member when torque is interrupted. Such couplings often comprise an outer race concentrically disposed with respect to an inner race, the outer race having cammed surfaces that define a pocket in which coupling rollers are assembled.
A driving member is connected to one race, and a driven member is connected to the other race. During torque transfer from the driving member to the driven member, the rollers become locked with a camming action against the cam surfaces, thereby establishing a positive driving connection between the driving member and the driven member. When the torque is interrupted, the driven member may freewheel relative to the driving member as the rollers become unlocked from their respective cam surfaces.
Another common overrunning coupling includes inner and outer races wherein one race is connected to a driving member and the other race is connected to the driven member. Overrunning coupling sprags are disposed between the inner cylindrical surface of the outer race and the outer cylindrical surface of the inner race so that the sprags lock the races together as torque is delivered to the driven member. The sprags become unlocked with respect to the inner and outer race surfaces when torque transfer is interrupted.
U.S. Pat. No. 5,927,455 discloses a bi-directional overrunning pawl-type clutch having a driving member mounted for power rotation, a driven member mounted for rotation adjacent the driving member, with each of the driving and driven members having pawl engaging shoulders, and a plurality of rigid pawls interposed between the driving and driven members. A control element is mounted for shifting movement between the driving and driven members to control the position of the pawls which are yieldably biased toward positions of engagement extending between the driving and driven members to produce driving engagement therebetween. The control element is shiftable to various positions to permit driving and overrunning in one direction or driving and overrunning in the opposite direction dependent upon the direction of rotation of the driving member.
U.S. Pat. No. 6,244,965 discloses a planar overrunning coupling for transfer of torque from a driving member to a driven member in one direction and which permits freewheeling motion between the members upon a torque reversal. The coupling includes coupling plates situated in close proximity with a strut retainer plate disposed between them. One plate is connected to the driving member and the other plate is connected to the driven member. Each plate has strut recesses. A series of struts is located in the recesses of one plate so that each strut may be pivoted, thereby allowing the struts to engage the companion recesses in the other coupling plate. The retainer has angularly spaced apertures that register with the struts to permit pivotal movement of the struts when the retainer plate is in one rotary position. The retainer plate, when it is in a second rotary position, prevents pivotal motion of the struts, thereby permitting freewheeling relative motion of the coupling plates.
U.S. Pat. No. 6,116,394 discloses an overrunning coupling assembly including a notch plate and an annular coupling pocket plate positioned in face-to-face relationship with respect to each other along a common axis. The pocket plate includes strut pockets disposed at angularly spaced positions about the axis. The notch plate includes notch recesses at angularly spaced positions about the common axis and positioned in juxtaposed relationship with respect to the strut pockets. The notch plate includes an inner circumferential rail at a radially inward side of the notch recesses and an outer circumferential rail at a radially outward side of the notch recesses. Torque-transmitting struts are positioned in the strut pockets. Each strut has first and second ears at one edge thereof for enabling pivotal motion of the struts about an ear axis intersecting the ears. The opposite edge of each strut is engageable with one of the notch recesses whereby one-way torque transfer may occur between the plates. Each opposite edge has first and second corners. Each strut pocket is sufficiently enlarged to allow pivotal movement of each strut about a strut axis which is parallel with the common axis, thereby enabling one of the first and second corners to be selectively supported by one of the inner and outer circumferential rails to prevent the struts from slapping against the notch recesses as the notch plate and pocket plate are respectively counterrotated.
U.S. Pat. No. 5,964,331 discloses a one-way clutch comprising a pocket plate and a notch plate situated in a juxtaposed adjacent relationship. One-way clutches of this kind are sometimes referred to as planar clutches because the adjacent juxtaposed surfaces are situated in radial planes with respect to the axis of the clutch.
For purposes of this disclosure, the term coupling should be interpreted to include clutches or brakes wherein one of the plates is drivably connected to a torque delivery element of a transmission and the other plate is drivably connected to another torque delivery element or is anchored and held stationary with respect to a transmission housing. The terms coupling, clutch and brake may be used interchangeably.
A pocket plate may be provided with angularly disposed recesses or pockets about the axis of a one-way clutch. The pockets are formed in the planar surface of the pocket plate. Each pocket receives a torque transmitting strut, one end of which engages an anchor point in a pocket of the pocket plate. An opposite edge of the strut, which may hereafter be referred to as an active edge, is movable from a position within the pocket to a position in which the active edge extends outwardly from the planar surface of the pocket plate. The struts may be biased away from the pocket plate by individual springs.
A notch plate may be formed with a plurality of recesses or notches located approximately on the radius of the pockets of the pocket plate. The notches are formed in the planar surface of the notch plate.
Another example of an overrunning planar clutch is disclosed in U.S. Pat. No. 5,597,057.
Other U.S. patents related to the present invention include: U.S. Pat. Nos. 5,070,978; 5,449,057; 5,806,643; 5,871,071; 5,918,715; 5,979,627; 6,065,576; 6,125,980; 6,129,190; 6,186,299; 6,193,038; 6,386,349; 6,481,551; 6,505,721; 6,571,926; and 6,854,577.
It is often desirable to have opposed engaging struts in a selectable or controllable clutch or coupling assembly so that torque can be transferred in both directions about an axis. It is also desirable to have an overrunning or free-wheeling capability in such clutches or assemblies. One way to control such sets of opposed struts or keys is to provide two slide or control plates. However, two slide plates add cost and complexity to the selectable clutch. In addition, such plates are more difficult to control external to the clutch.